518 Traksactioxs of the American Institute. 



This slicing can be done by slightly changing an ordinary root cutting 

 machine to serve the purpose. 



The potatoes thus sliced will be read}^ for drying or desiccation ; 

 and the construction of the kiln for their reception, will be found of 

 very great importance in securing a high grade of excellence in the 

 desiccated material. 



The most common form of kiln is that heated simply by a stove 

 and provided with perforated shelves or drawers for holding the sub- 

 stance to be dried, or with a slatted floor covered with a coarse, loose 

 cloth, and designed for the same purpose. Many different apparatus 

 have been made on this principle for drying fruit, and such a one 

 would probably answer well for preparing the sweet potato on a 

 small scale, but would be too slow and variable in its operation for 

 extended use. Another method differs. from that just mentioned in 

 this, that the air is heated by external means and instead of moving 

 upward, is caused by a suitable arrangement of flues, to pass down- 

 ward through the material to be dried. This prevents the moisture 

 with which the air may sometimes become surcharged from being 

 condensed upon or reabsorbed by the material. 



There is a third plan, also involving the use of hot air, and which 

 has been tried with success in desiccating the common or Irish potato. 

 It consists in rapidly forcing streams of heated air through the mass 

 of material by mechanical means. The air takes up the moisture 

 very quickly from the mass and carries it away. This appears to be 

 the most eflicient of all the hot air methods, and the only objections 

 that can be urged against it are the possibility of heating the air so 

 hot as to injure the substance when nearly dry. The expense of 

 the appliances required to produce the air blast, and the great 

 loss of heat resulting from the liigli temperature at which the 

 air leaves the kiln, is large. To obviate some, at least, of these 

 drawbacks the writer would suggest a method, which, as far as he is 

 aware, has never been put in practice for the purpose. This consists 

 simply in evaporating the moisture from the material in vacuo, by 

 which the heat need not be rnised to more than 150 deg. or IGO deg. 

 Fahrenheit to secure it? thorough expulsion. The heat should be 

 applied externally to a drying chamber furnished inside with slatted 

 shelves, or preferably with a rotating reticulated cylinder, for holding 

 the sliced material, the air, and also the steam as fast as generated, being 

 drawn oft' from the drying chamber by appropriate mechanism, in the 

 same manner as from the vacuum pan of a sugar apparatus. The 



